Generally, ophthalmic lenses are manufactured on automated production lines, which include various production steps and inspection steps. In the process of manufacturing ophthalmic lenses commonly referred to as contact lenses, the lenses are inspected at various stages of its manufacture. Inspecting the lenses enables identification of defects, if any. Such inspection at different stages of manufacture not only enables removal of defective items before shipment to a customer, but also enables rectification of the process problems through analysis of the defective items, which in turn results in improvement in quality and also significant savings in terms of time and effort. One such stage at which the contact lenses are inspected is after the contact lens is cast-molded in molds. At this stage, the contact lens is inspected to identify existence of defects such as, bubbles in the polymer of clear and printed contact lens, print smear in the case of printed contact lens, in addition to any other defects encountered in a contact lens.
Colored or printed contact lens enhances the beauty of the eyes of the user. As the market volumes for such lenses are large, it is required to produce these lenses in large volumes using automated systems. In spite of high-production volumes, it is critical that quality is maintained as these contact lenses make physical contact with the eyes. A number of systems exist today that inspect the lenses after the cast-molding process. Traditional systems require one of the molds to be disengaged or removed to provide an open zone for an inspection system to be positioned above the lenses for capturing images of the complete lens. This process increases the time to inspect the finished product and it becomes difficult to differentiate whether defects existed before or after the disengagement of one of the molds.
Other prior-art systems exist that inspect the contact lens when it is within the mold assembly. Such systems include an illumination system, imaging optical system, and camera. In such prior-art systems, direct light rays illuminate the contact lens, and the light rays emerging from the contact lens are captured by the imaging optical system to generate an image of the contact lens. The entrance pupil of the image optical system, in prior-art systems, is located near or behind the lens of the image optical system and is far away from the mold case. The resulting image will allow inspection of only a portion (center zone) of the contact lens. The light emerging from a peripheral zone of the contact lens cannot reach the imaging optical system because a certain part of the case of the male mold blocks the light rays emerging from the peripheral zone.